mitosis

• All cells are derived from preexisting cells
(Cell Theory)
• Cell division is the process by which cells
produce new cells
• Cells grow in number, NOT in
size
– Smaller cells more efficient
(cellular transport, cellular
communication/signaling)
– Easier to take in nutrients &
get rid of wastes
• Some cells must be repaired often such as
cells lining the intestines, white blood cells,
skin cells with a short lifespan
• Other cells DO NOT divide at all after birth
such as muscle, nerve cells, brain cells,
female egg cells
• Cell growth
• Repair & replacement of damaged cell parts
• Growth and development of an embryo
• The plans for making cells are coded in DNA
• DNA, deoxyribose nucleic acid, is a long thin
molecule that stores genetic information
• DNA is organized into giant molecules called
chromosomes
• Chromosomes are
made of protein & a
long, single, tightlycoiled DNA molecule
visible only when
the cell divides
• When a cell is NOT
dividing the
chromosome (DNA)
is less visible & is
called chromatin
• Centromeres hold duplicated
chromosomes together
before they are separated in
mitosis
• When DNA makes copies of
itself before cell division,
each half of the chromosome
is called a sister chromatid
– Each sister chromatid
contains identical genetic
information
• Eukaryotes (nucleus & membrane-bound
organelles) must be copied exactly so the 2
new cells formed from division will be
exactly alike
– The original parent cell & 2 new daughter
cells must have IDENTICAL chromosomes
– Ex: Humans have 46 chromosomes in our
somatic cells (body cells). After one of
these somatic cells goes through mitosis, 2
daughter cells are produced each having
46 chromosomes (genetically identical).
• Both the nucleus (mitosis) and the
cytoplasm (cytokinesis) must be divided
during cell division in eukaryotes
• Cells go through phases or a cell cycle
during their life before they divide to
form new cells
–Cell cycle is about 12-24 hrs. for
most animal cells
–Cell cycle is controlled by proteins and
enzymes
• The cell cycle includes 3 main parts --interphase, mitosis, and cytokinesis
– mitosis = nuclear division
– cytokinesis = division of the cytoplasm
• Interphase is the longest part of a cell's life
cycle and is called the "resting stage"
because the cell isn't dividing
Animal Cell
Plant Cell
Nucleus
• Divided into 3 stages:
1) G1 (Gap 1) = cell is growing, carrying out
normal cell functions, preparing to replicate
DNA
– Cells mature & increase in size by making
more cytoplasm & organelles
2) S (synthesis) = DNA is copied or replicated
– DNA is in the form of chromatin (uncoiled
DNA) and is NOT visible
3) G2 (Gap 2) =cell prepares for nuclear
division (mitosis)
– cells makes all the structures needed to
divide
Centrioles
Nucleolus
Cell
membrane
Nucleus
• Division of the nucleus or mitosis occurs
first
• Mitosis is an asexual method of reproduction
– Only one parent cell
– Daughter cells have SAME number of
chromosomes (genetic info.)
• Mitosis consists of 4 stages --- prophase,
metaphase, anaphase, & telophase
• Longest phase of MITOSIS
• Chromatin (uncoiled DNA) condenses and
coils into the form of chromosomes
– chromosomes are visible (shaped like a “X”)
• Sister chromatids (half of a “X”) attach to
each other by the centromere
• Centrioles in animal cells move to opposite
ends of cell
• Spindle forms from each centriole (ONLY in
animal cells)
– Plant cells DO NOT have centrioles
(spindle forms from a microtubule)
• Nuclear membrane dissolves (disappears)
• Nucleolus disintegrates
Animal Cell
Chromosomes
Plant Cell
Spindle
Fibers
Centrioles
Centromere
Chromosome
• Shortest phase of MITOSIS
• Chromosomes line up in center or equator of
the cell
• the centromere of each chromosome
attaches to spindle fibers
Animal Cell
Spindle fibers
Plant Cell
Chromosome
• Spindle fibers attached to the centriole pull
the sister chromatids apart at their
centromere
• Separated chromosomes travel along the
spindle fibers to the two poles (ends) of the
cell.
Sister chromatids
Animal Cell
Sister chromatids
Plant Cell
Sister Chromatids
(genetically identical)
• Nuclear membrane forms at each end of the
cell around the chromosomes
• Nucleolus reforms
• Spindle fibers begin to break down
• Chromosomes become less tightly coiled &
appear as chromatin again
• Cytokinesis begins
Animal Cell
Plant Cell
Nuclear
membrane
(forming)
DNA uncoilingbecoming
chromatin
Nucleolus
(forming)
• Cytokinesis = division of the cytoplasm
of the cell and its organelles separate
into 2 new daughter cells
2 new daughter cells
(genetically IDENTICAL)
• In animals, a groove
called the cleavage
furrow forms
pinching the parent
cell in two
• In plants, a cell plate forms down the
middle of the cell where the new cell
wall will be
2 new daughter cells
(genetically IDENTICAL)
• Cell division must be controlled, otherwise
cell growth will occur without limit (cancer)
– DNA mutations lead to changes in the
proteins/enzymes that regulate the cell
cycle
Cancerous Kidney Cells
• Cancer = a cell or group of cells that grow
out of control and create a tumor
• Crowds out normal cells and results in
the loss of tissue function
Cancerous Kidney Cells
– Tumor = mass of growing, unregulated cells
• 2 types of tumors:
1. Benign- tumor that does not
spread
2. Malignant- tumor that spreads and
destroys healthy tissue
• Genetics (family history)
• Smoking
• Carcinogens (cancer-causing chemicals)
• Viruses:
– HPV can lead to cancer of reproductive
organs
• Radiation:
• Sunlight- skin cancer
What phase of the cell cycle would
this be?
• PROPHASE
http://www.jburroughs.org/science/resources/mitosis/cellcycle.html
What phase of the cell cycle would
this be?
• ANAPHASE
http://www.jburroughs.org/science/resources/mitosis/cellcycle.html
What phase of the cell cycle would
this be?
• INTERPHASE
http://www.jburroughs.org/science/resources/mitosis/cellcycle.html
What phase of the cell cycle would
this be?
• TELOPHASE
http://www.jburroughs.org/science/resources/mitosis/cellcycle.html
What phase of the cell cycle would
this be?
• METAPHASE
http://www.jburroughs.org/science/resources/mitosis/cellcycle.html
http://district.bluegrass.kctcs.edu/billd.snyder/sharedfiles/biowebsite/BiologyLabs/BIO137/1
37Lab2/Lab2MitosisSlides.html